JPH0652043B2 - Manufacturing method for apex seal of rotary piston engine - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for manufacturing an apex seal for a rotary piston engine, and particularly to Si ₃ N excellent in initial conformability.
_{The present} invention relates to a method for manufacturing an apex seal made of No. ₄ .

(Prior Art) Conventionally, a chilled alloy cast iron has been used as an apex seal of a rotary piston engine, and exhibits excellent sliding characteristics with Cr plating applied to a trochoid surface of a rotor housing.

In order to improve the initial conformability of the sliding surface and trochoidal surface of the apex seal at the beginning of use of the rotary piston engine, at present, by blasting fine particles of carborundum on the sliding surface of the apex seal, the cast iron chill A method of roughening the surface roughness is adopted.

By the way, in recent years, vigorous research has been conducted on the use of fine ceramic materials as engine sealing materials (for example, apex seals in rotary piston engines) because of their excellent wear resistance at high temperatures.

Among them, Si ₃ N ₄ is considered to be the most superior candidate for the sealing material because it has properties such as excellent wear resistance, strength at high temperature and toughness, and resistance to thermal shock. There is.

(Problems to be Solved by the Invention) By the way, in the case of an apex seal made of Si ₃ N ₄ , S
Since i ₃ N ₄ has excellent wear resistance and high strength, there is a problem in that initial conformability at the beginning of use of the rotary piston engine is poor and the engine compression reduction rate is large, resulting in a reduction in engine output.

Therefore, as is commonly done for metal seal materials and the like, fine particles such as green carborundum (SiC) can be shot blasted on the sliding surface of an apex seal made of Si ₃ N ₄ to make it porous. It is conceivable that the sliding surface cannot be made even and fine in this case, and the sliding surface peels off due to the impact of shot blasting so that the sliding surface has a uniform surface roughness. Cannot be formed.

Further, it is possible to perform electrolytic etching on the sliding surface of the apex seal, but the etching method cannot be applied because ordinary Si ₃ N ₄ is an insulator.

(Means for Solving Problems) A method for manufacturing an apex seal for a rotary piston engine according to the present invention is to manufacture an apex seal material composed of Si ₃ N ₄ and a predetermined amount of conductive particles dispersedly contained in Si ₃ N _4. Then, the sliding surface of this apex seal material is subjected to electrolytic discharge treatment to decompose and eliminate the conductive particles, thereby making the sliding surface porous.

As the conductive particles, at least 50 (1 / Ω · c
It is necessary that the material has an electric conductivity of m) or more and is excellent in high temperature stability and corrosion resistance. Carbides such as Ti, SI and Ta, nitrides, borides (for example, TiN, TiB ₂ ,
TiC, SiC, TaN, etc.) can be used.

The amount of the conductive particles added is not particularly limited because the electrical conductivity varies depending on the material of the conductive particles, but the apex seal material composed of Si ₃ N ₄ and the conductive particles is as follows. It is desirable to have such characteristics.

(1) Electric conductivity ≧ 50 (1 / Ω · cm), (2) Normal temperature bending strength ≧ 80 (kg / mm ² ), (3) Rockwell hardness HRA ≧ 85, electric conductivity is above (1) When the condition (4) is not satisfied, the electrolytic discharge property during electrolytic discharge treatment is poor, the porous surface of the sliding surface of the apex seal becomes insufficient, and the required surface roughness Ra ≧ 1.0 μ cannot be obtained.

Room temperature bending strength and Rockwell hardness are (2) and
If the condition (3) is not satisfied, the wear resistance at high temperature originally possessed by Si ₃ N ₄ will be impaired.

Therefore, it is desirable to add the conductive particles in an amount of about 5 to 25% by weight.

(Operation) In the method for manufacturing an apex seal for a rotary piston engine according to the present invention, the apex seal material has conductivity due to the conductive effect of the predetermined amount of conductive particles dispersedly contained in Si ₃ N ₄ as described above. When the sliding surface of this apex seal material is subjected to electrolytic discharge treatment, the conductive particles on the sliding surface are dispersed and disappear, and the sliding surface becomes a fine porous shape.

When the sliding surface of the apex seal is made porous in this way, the sliding surface comes into sliding contact with the trochoidal surface made of the sprayed layer such as Cr ₃ C _{2 on} the inner circumference of the rotor housing at the beginning of use of the rotary piston engine. The surface pressure and shearing force of the innumerable fine projections are significantly increased and worn, the initial conformability of the sliding surface is significantly improved, and the sealing property is improved.

(Effects of the Invention) According to the method for manufacturing an apex seal for a rotary piston engine according to the present invention, as described above, the apex containing Si ₃ N ₄ as a main component by dispersing and containing a predetermined amount of conductive particles. The sliding surface of the apex seal is made even and finely porous by a very simple method of giving conductivity to the sealing material and subjecting the sliding surface to electrolytic discharge treatment, and the initial conformability of the sliding surface of the apex seal It is possible to significantly improve the engine output and achieve higher engine output.

(Example) Hereinafter, the Example of this invention is described based on drawing.

As shown in FIGS. 1 and 2, the rotary piston engine E has a rotor 3 arranged in a rotor housing chamber formed by a rotor housing 1 and side housings 2 arranged on both sides of the rotor housing 1. Sealing material such as apex seal 4 on the top and trochoidal surface 5 on the inner surface of rotor housing 1
The three working chambers 6 are partitioned by and, and the rotor 3 is eccentrically rotated, so that the output shaft 11 is driven by sequentially repeating the steps of intake, compression, explosion, and exhaust in each working chamber 6. Therefore, the apex seal 4 comes into sliding contact with the trochoidal surface 5 as the rotor 3 rotates, comes into contact with high-temperature combustion gas, and is exposed to the intense thermal shock associated with suction and explosion. .

As shown in FIG. 2, the apex seal 4 is disposed in the seal mounting groove 7 at the top of the rotor 3, and is elastically biased toward the trochoidal surface 5 by the apex seal spring 8 so that one end of the apex seal 4 is Is obliquely divided, and the end face of the side piece 4b of the apex seal 4 is moved to the side housing 2 by the relative movement on this divided surface.
It comes in sliding contact with the surface (including the center housing).

The manufacturing method of the apex seal 4 is as follows.

A small amount of sintering aids (MgO, Ce) of Si ₃ N ₄ powder.
O, and the like ZrO _2), from about 5 to 25 wt% of the conductive particles _{(TiN, TiB 2, TiC,} SiC, TaN , etc.) were mixed, the mixed powder of ordinary sintering method (HIP, hot After being sintered by pressing, normal pressure sintering, etc.), the apex seal material 4A having a predetermined shape is manufactured by polishing with a diamond grindstone.

Next, a masking paint 10 is applied to the portion other than the sliding surface 4a of the apex seal material 4A to mask it, and the apex seal material 4A is dipped in an electrolytic solution as shown in FIG. 4a neighborhood 10
A graphite electrode 9 is arranged at a position of mm, and the sliding surface 4a is formed by using the apex seal material 4A as a positive pole and the graphite electrode 9 as a negative pole.
Is subjected to electrolytic discharge treatment.

By this electrolytic discharge treatment, the sliding surface 4 of the apex seal 4
As shown in FIG. 4 and FIG. 5, a is uniformly and finely porous (made porous).

Hereinafter, specific examples will be described.

(1) The composition of the above-mentioned mixed powder (however, shown in% by weight) is
_{Si 3 N 4: 86%,} MgO: 2%, CeO: 2%, T
iN: 10%.

(2) Sintering is carried out by hot pressing, and the conditions are
Pressing pressure: 200 kg / cm ² , temperature: 1750 ° C., time:
It was 2 hours.

(3) The sintered body after the above-mentioned sintering was polished with a diamond grindstone to obtain an apex seal material 4A having a predetermined shape.

(4) Masking paint 10 was applied to the portion other than the sliding surface 4a of the Apx seal material 4A to mask it.

(5) The electrolytic discharge treatment uses an electrolyte solution of 10% KOH and a graphite electrode 9 (-electrode), current: 0.3 A, voltage: 50 V,
Time: It carried out on condition of 10 minutes. However, the gap between the sliding surface 4a of the apex seal material 4A and the graphite electrode 9 is 10
mm.

Surface roughness R _a of the sliding surface 4a of the apex seal 4 fabricated as described above, before electrochemical discharge process Ra =
While it was 0.2 μ, after the electrolytic discharge treatment, Ra =
It was 1.0 to 3.0 μ.

Figure 6 is an electrical conductivity of the apex seal material 4A, the surface roughness R _a of the sliding surface 4a after electrolysis discharge treatment
It was obtained experimentally, and the surface roughness increases as the electrical conductivity increases. In order to secure the initial conformability of the apex seal 4, the surface roughness Ra is set to R.
It is desirable that a ≧ 1.0 μ, and for that purpose, the electric conductivity of the apex seal material 4A is at least 50.
It must be (1 / Ω · cm) or more.

Hereinafter, the product to which the present invention is applied and the product to which the present invention is applied manufactured by the method of the above-mentioned embodiment, a comparative example manufactured in the same manner as above and not subjected to electrolytic discharge treatment, and electrolytic discharge manufactured only with Si ₃ N ₄ and a sintering aid. The test results of the comparative example which is not treated will be described.

FIG. 7 shows the results of a compression down test performed by incorporating the above-described four types of apex seals 4 into an actual rotary piston engine.

The above compression down test is 700 at engine speed 1500 rpm and full load with accelerator fully open.
After increasing to 0 rpm, return the accelerator to 1500
The operation of lowering to rpm is defined as one test cycle, and this test cycle is repeated. The time required for one test cycle is 1 minute, the compression value (compressed gas pressure) is measured every three test cycles, and the initial conformability of the apex seal 4 is evaluated from the reduction rate. It shows that it is excellent in the initial familiarity.

The rotary piston engine subjected to the test is an exhaust quantity 1300cc × 140PS, the trochoid surface 5 of the rotor housing 1 sprayed layer of C _r3 C ₂ was formed to a thickness of 0.10～0.15Mm.

Following the Table 1, shows a surface roughness R _a and the compression-down test results for each sliding surface 4a of the four apex seal 4.

As is clear from FIG. 7 and Table 1 above, in the products to which the present invention is applied and the sliding surface 4a is uniformly and finely porous by the electrolytic discharge treatment, the surface roughness of the sliding surface 4a is compared. It becomes significantly larger than the examples and, thereby, the initial conformability becomes excellent, and it is noticeable in the result of the compression down test.

Next, for reference, Table 2 below shows the mechanical properties of the product of the present invention or a comparative example.

As described above, according to the preparation of apex seal according to the embodiment, compromising the properties the Si ₃ N ₄ made of apex seal by dispersing contain a small amount of conductive ceramic material in Si ₃ N ₄ no, the uniformly and finely porous the sliding surface 4a by electrochemical discharge process to impart conductivity to the apex seal material 4A, it can be porous the sliding surface 4a by a simple process, Si ₃ N It is possible to significantly improve the initial conformability of the apex seal ₄ containing ₄ as a main component.

[Brief description of drawings]

The drawings show an embodiment of the present invention. Fig. 1 is a longitudinal sectional view of a rotary piston engine, Fig. 2 is a sectional view taken along the line II-II in Fig. 1, and Fig. 3 shows electrolytic discharge treatment on an apex seal material. FIG. 4 is an exploded perspective view of the apex seal, FIG. 5 is an enlarged cross-sectional view of the main part of the apex seal, and FIG. 6 is electrical conductivity and roughness of the sliding surface after electrolytic discharge treatment. Fig. 7 is a diagram showing the relationship with the pressure Ra, and Fig. 7 is a diagram showing the relationship between the test cycle and the compression pressure decrease rate. 4 ... Apex seal, 4A ... Apex seal material, 4a ... Sliding surface.

Claims (2)

[Claims] 1. An apex seal material made of Si ₃ N ₄ and a predetermined amount of conductive particles dispersedly contained in the apex seal material is produced, and a sliding surface of the apex seal material is subjected to electrolytic discharge treatment to obtain conductive particles. A method for manufacturing an apex seal for a rotary piston engine, characterized in that the sliding surface is made porous by decomposing and disappearing. 2. The first amount of conductive particles is about 5 to 25% by weight TiN.
A method of manufacturing an apex seal for a rotary piston engine according to the paragraph.